The subject matter of the invention is a composition for dyeing hair containing a 4'-amino-2-halogen-4-[bis-(.beta.-hydroxyethyl)amino]azobenzene.
Along with oxidative hair dyes formed by oxidative coupling of one or more developers, direct-dyeing hair dyes are becoming increasingly important for dyeing hair. Direct hair dyes offer the advantage that they can be applied without the addition of oxidizing agents (for example hydrogen peroxide) and therefore cause considerably less damage to the hair during the dyeing process.
Good hair dye compositions must satisfy a number of requirements. For example, they must create the desired shade with sufficient intensity and at the same time be absorbed in the hair without excessive discoloration of the scalp. Further, the hair dyeing must possess sufficient fastness to light, heat, perspiration, hair cleaning agents, and the chemicals used for permanent waving. They must also be stable when acted on by acidic agents and diluted acids. Finally, these compositions should be unobjectionable in toxicological and dermatological respects.
Since a uniform coloring of the hair from the root to the tip of the hair is generally impossible with dyes of a single class of compounds, combinations of dyes from a number of different classes of compounds are normally used--for example, dye combinations containing azo and anthraquinone dyes in addition to derivatives of amino-, diamino-, and hydroxyamino-nitrobenzenes.
The most commonly used azo dye is 4'-amino-4-[bis-(.beta.-hydroxyethyl)amino]azobenzene (DISPERSE BLACK 9). It is also known from DE-OS 35 34 885 to use 4'-amino-2-methyl-4[bis-(.beta.-hydroxyethyl)amino]azobenzene as a hair dye.
Although often used in hair dye compositions, the 4'-amino-4-[bis-(.beta.-hydroxyethyl)amino]azobenzene is not completely satisfactory in technical respects relating to application. On the one hand, this compound is suspected of mutagenic behavior. On the other hand, hair dyeing produced by this compound and by the hair dyes known from DE-OS 35 34 885 have a poor stability relative to acids and acidic preparations.